Heat staking process with increased retention force

ABSTRACT

A heat staking method and apparatus is provided for use in deforming a heat-stake so that it becomes mechanically coupled to an encapsulate. The deformed portion of the heat-stake contacts a retention component that provides additional composition strength and fastening surface to the encapsulate.

This application claims priority to U.S. Ser. No. 60/877,744, entitledIncreased Molding Retention to Injected Material, filed Dec. 29, 2006,now abandoned, which is incorporated herein by reference.

I. BACKGROUND OF THE INVENTION

A. Field of Invention

This invention pertains to the art of methods and apparatuses regardingthe manufacture and assembly of plastic components, and moreparticularly to methods and apparatuses regarding the heat staking of aplastic molding.

B. Description of the Related Art

With reference to FIGS. 9-10, it is known in the automotive industry touse a heat stalking process to join automotive parts. In one knownapplication, a plurality of first thermoplastic components, commonlyreferred to as heat-stakes 64, may be located sporadically around theperiphery of a first automotive part 60 and a second automotive part 62may comprise a plurality of second thermoplastic components, commonlyreferred to as encapsulates 66, comprising receiving holes 68 located incorresponding locations to the heat-stakes of the first automotive part60. The heat-stakes 64 may be inserted into the receiving holes 68 ofthe corresponding encapsulates 66 and a staking device (not shown) maybe used to heat-treat a leading end 65 of each heat-stake 64. This useof the staking device results in the deformation of the heated leadingend of the heat-stake such that a “mushroom cap” 67 may be formed. Themushroom cap 67 of each heat stake 64 commonly covers the correspondingreceiving hole 68 of the encapsulate 66. This resulting overlap resultsin the mechanical coupling of the first and second automotive parts 60,62. It is known that the resulting retention force of any heat stakingprocess may be dependent upon the amount of surface area of theencapsulate 66 contacted by the heat-stake's mushroom cap 67 as well asthe composition states of the encapsulate 66 and heat-stake 64. By“retention force” it is meant the force required to separate, break, orundo the mechanical coupling created by the heat staking process.

Although many known methods of heat staking work well for their intendedpurposes, various disadvantages exist. One disadvantage relates to thefastening surface of the encapsulate available to contact the mushroomcap of the heat-stake. Commonly the fastening surface available isrelatively small. Additionally, the process of heating the leading endof the heat-stake may further reduce the amount of fastening area. Whenan encapsulate is comprised of a softer composition than that of theheat-stake, the small amount of surface area available for theheat-stake's mushroom head to contact may be insufficient to achieve ahigh retention force. Often, the heat from the heat staking processtends to melt some of the encapsulate's softer material. This meltingmay create a loose condition that may further reduce retention force.

What is needed, therefore, is a heat staking process that increasesretention force by increasing the amount of fastening area available tocontact with the heat-stakes' mushroom cap while also increasing theretention characteristics of the encapsulate.

II. SUMMARY OF THE INVENTION

According to one embodiment of this invention, a method comprises thesteps of: providing a thermoplastic encapsulate comprising at least afirst opening; attaching a retention component to the thermoplasticencapsulate; inserting a thermoplastic heat stake having a first endthrough the first opening so that the first end extends through thefirst opening; heating the first end of the thermoplastic heat stake;and, deforming the first end of the thermoplastic heat stake to overlapor surround at least part of the retention component.

According to another embodiment of this invention, a method comprisesthe steps of: providing a thermoplastic encapsulate comprising at leasta first opening; attaching a retention component to the first opening ofthe thermoplastic encapsulate; inserting a thermoplastic heat stakehaving a first end through the first opening so that the first endextends through the first opening; heating the first end of thethermoplastic heat stake; and, deforming the first end of thethermoplastic heat stake to overlap or surround at least part of theretention component.

According to another embodiment of this invention, a method comprisesthe steps of: providing a thermoplastic encapsulate comprising at leasta first opening; forming a retention component of a composition that isharder than the thermoplastic encapsulate; attaching a retentioncomponent to the thermoplastic encapsulate; inserting a thermoplasticheat stake having a first end through the first opening so that thefirst end extends through the first opening; heating the first end ofthe thermoplastic heat stake; and, deforming the first end of thethermoplastic heat stake to overlap or surround at least part of theretention component.

According to another embodiment of this invention, a method comprisesthe steps of: providing a thermoplastic encapsulate comprising at leasta first opening; forming a retention component of a thermoplastic;attaching a retention component to the thermoplastic encapsulate;inserting a thermoplastic heat stake having a first end through thefirst opening so that the first end extends through the first opening;heating the first end of the thermoplastic heat stake; and, deformingthe first end of the thermoplastic heat stake to overlap or surround atleast part of the retention component.

According to another embodiment of this invention, a method comprisesthe steps of: providing a thermoplastic encapsulate comprising at leasta first opening; forming a retention component of a thermoplastic;attaching a retention component to the thermoplastic encapsulate usingan over-molding process; inserting a thermoplastic heat stake having afirst end through the first opening so that the first end extendsthrough the first opening; heating the first end of the thermoplasticheat stake; and, deforming the first end of the thermoplastic heat staketo overlap or surround at least part of the retention component.

According to another embodiment of this invention, a method comprisesthe steps of: providing a thermoplastic encapsulate comprising at leasta first opening; forming a retention component of a thermoplastic;attaching a retention component to the thermoplastic encapsulate using aco-injection molding process; inserting a thermoplastic heat stakehaving a first end through the first opening so that the first endextends through the first opening; heating the first end of thethermoplastic heat stake; and, deforming the first end of thethermoplastic heat stake to overlap or surround at least part of theretention component.

According to one embodiment of this invention, a method comprises thesteps of: providing a thermoplastic encapsulate comprising at least afirst opening; attaching a retention component to the thermoplasticencapsulate; forming a thermoplastic heat stake of a composition that isharder than the thermoplastic encapsulate; inserting a thermoplasticheat stake having a first end through the first opening so that thefirst end extends through the first opening; heating the first end ofthe thermoplastic heat stake; and, deforming the first end of thethermoplastic heat stake to overlap or surround at least part of theretention component.

According to another embodiment of this invention, a method comprisesthe steps of: providing a thermoplastic encapsulate comprising at leasta first opening; attaching a retention component to the thermoplasticencapsulate; forming a thermoplastic heat stake of a composition thathas a higher melting point than the thermoplastic encapsulate; insertinga thermoplastic heat stake having a first end through the first openingso that the first end extends through the first opening; heating thefirst end of the thermoplastic heat stake; and, deforming the first endof the thermoplastic heat stake to overlap or surround at least part ofthe retention component.

According to one embodiment of this invention, a method comprises thesteps of: providing a first automotive part comprising at least a firstthermoplastic encapsulate having a first opening; attaching a firstretention component to the first thermoplastic encapsulate adjacent tothe first opening; providing a second automotive part comprising atleast a first thermoplastic heat stake having a first end; inserting thefirst thermoplastic heat stake through the first opening so that thefirst end extends through the first opening; heating the first end ofthe thermoplastic heat stake; and, deforming the first end of thethermoplastic heat stake to at least partially overlap the retentioncomponent.

According to another embodiment of this invention, a method comprisesthe steps of: providing a first automotive part comprising at least afirst thermoplastic encapsulate having a first opening; forming a firstretention component of a composition that is harder than the firstthermoplastic encapsulate; attaching the first retention component tothe first thermoplastic encapsulate adjacent to the first opening;providing a second automotive part comprising at least a firstthermoplastic heat stake having a first end; inserting the firstthermoplastic heat stake through the first opening so that the first endextends through the first opening; heating the first end of thethermoplastic heat stake; and, deforming the first end of thethermoplastic heat stake to at least partially overlap the retentioncomponent.

According to another embodiment of this invention, a method comprisesthe steps of: providing a first automotive part comprising at least afirst thermoplastic encapsulate having a first opening; attaching afirst retention component to the first thermoplastic encapsulateadjacent to the first opening; forming a thermoplastic heat stake of acomposition that has a higher melting point than the thermoplasticencapsulate; providing a second automotive part comprising at least thefirst thermoplastic heat stake having a first end; inserting the firstthermoplastic heat stake through the first opening so that the first endextends through the first opening; heating the first end of thethermoplastic heat stake; and, deforming the first end of thethermoplastic heat stake to at least partially overlap the retentioncomponent.

According to another embodiment of this invention, a method comprisesthe steps of: providing a first automotive part comprising at least afirst thermoplastic encapsulate having a first opening; forming athermoplastic heat stake of a composition that has a higher meltingpoint than the thermoplastic encapsulate; attaching a first retentioncomponent to the first thermoplastic encapsulate adjacent to the firstopening; providing a second automotive part comprising at least a firstthermoplastic heat stake having a first end; inserting the firstthermoplastic heat stake through the first opening so that the first endextends through the first opening; heating the first end of thethermoplastic heat stake; and, deforming the first end of thethermoplastic heat stake to at least partially overlap the retentioncomponent.

According to another embodiment of this invention, a method comprisesthe steps of: providing a first automotive part comprising at least afirst thermoplastic encapsulate having a first opening; attaching afirst retention component to the first thermoplastic encapsulate suchthat the first retention component substantially encircles the firstopening; providing a second automotive part comprising at least a firstthermoplastic heat stake having a first end; inserting the firstthermoplastic heat stake through the first opening so that the first endextends through the first opening; heating the first end of thethermoplastic heat stake; and, deforming the first end of thethermoplastic heat stake to at least partially overlap the retentioncomponent.

According to one embodiment of this invention, a method comprises thesteps of: providing a first automotive part comprising at least a firstthermoplastic encapsulate having a first opening; forming a firstretention component of a thermoplastic; attaching the first retentioncomponent to the first thermoplastic encapsulate adjacent to the firstopening; providing a second automotive part comprising at least a firstthermoplastic heat stake having a first end; inserting the firstthermoplastic heat stake through the first opening so that the first endextends through the first opening; heating the first end of thethermoplastic heat stake; and, deforming the first end of thethermoplastic heat stake to at least partially overlap the retentioncomponent.

According to another embodiment of this invention, a method comprisesthe steps of: providing a first automotive part comprising at least afirst thermoplastic encapsulate having a first opening; forming a firstretention component of a thermoplastic; attaching the first retentioncomponent to the first thermoplastic encapsulate adjacent to the firstopening using an over-molding process; providing a second automotivepart comprising at least a first thermoplastic heat stake having a firstend; inserting the first thermoplastic heat stake through the firstopening so that the first end extends through the first opening; heatingthe first end of the thermoplastic heat stake; and, deforming the firstend of the thermoplastic heat stake to at least partially overlap theretention component.

According to another embodiment of this invention, a method comprisesthe steps of: providing a first automotive part comprising at least afirst thermoplastic encapsulate having a first opening; forming a firstretention component of a thermoplastic; attaching the first retentioncomponent to the first thermoplastic encapsulate adjacent to the firstopening using a co-injection molding process; providing a secondautomotive part comprising at least a first thermoplastic heat stakehaving a first end; inserting the first thermoplastic heat stake throughthe first opening so that the first end extends through the firstopening; heating the first end of the thermoplastic heat stake; and,deforming the first end of the thermoplastic heat stake to at leastpartially overlap the retention component.

According to one embodiment of this invention, a vehicle comprises afirst automotive part and a second automotive part. The first automotivepart comprises a first thermoplastic encapsulate having a first openingand a first retention component adjacent to the first opening. Thesecond automotive part comprises a first thermoplastic heat stake thatcomprises a first end. The thermoplastic heat stake is received withinthe first opening of the first automotive part such that the first endextends through the first opening. When the first end of the firstthermoplastic heat stake is heated, the first end of the firstthermoplastic heat stake deforms to at least partially cover the firstretention component and to form a mechanical coupling of the firstautomotive part to the second automotive part.

According to another embodiment of this invention, a vehicle comprises afirst automotive part and a second automotive part. The first automotivepart comprises a first thermoplastic encapsulate having a first openingand a first retention component adjacent to the first opening and asecond thermoplastic encapsulate having a second opening and a secondretention component. The second automotive part comprises a firstthermoplastic heat stake that comprises a first end and a secondthermoplastic heat stake that comprises a second end. The first andsecond thermoplastic heat stakes are received within the first andsecond opening of the first automotive part such that the first endextends through the first opening and the second end extends through thesecond opening. When the first and second ends of the first and secondthermoplastic heat stakes are heated, the first and second ends of thefirst and second thermoplastic heat stakes deform to at least partiallycover the first and second retention components respectively and to forma mechanical coupling of the first automotive part to the secondautomotive part.

According to one embodiment of this invention, a vehicle comprises afirst automotive part and a second automotive part. The first automotivepart comprises a first thermoplastic encapsulate having a first openingand a first retention component adjacent to the first opening. Thesecond automotive part comprises a first thermoplastic heat stake thatcomprises a first end. The thermoplastic heat stake is received withinthe first opening of the first automotive part such that the first endextends through the first opening. When the first end of the firstthermoplastic heat stake is heated, the first end of the firstthermoplastic heat stake deforms to substantially cover the firstretention component and to form a mechanical coupling of the firstautomotive part to the second automotive part.

According to one embodiment of this invention, a vehicle comprises afirst automotive part and a second automotive part. The first automotivepart comprises a first thermoplastic encapsulate having a first openingand a first retention component adjacent to the first opening. Thesecond automotive part comprises a first thermoplastic heat stake thatcomprises a first end. The thermoplastic heat stake is received withinthe first opening of the first automotive part such that the first endextends through the first opening. When the first end of the firstthermoplastic heat stake is heated, the first end of the firstthermoplastic heat stake deforms to at least partially cover the firstretention component without the first thermoplastic heat stakecontacting the first thermoplastic encapsulate and to form a mechanicalcoupling of the first automotive part to the second automotive part.

One advantage of this invention is that the retention component providesan increased retention force for the mechanical coupling of parts.

Another advantage of this invention is that the retention component maybe comprised of a different composition than that of either theencapsulate or the heat-stake. This allows a person of skill in the artto choose the specific composition of the retention component based on avariety of factors and considerations, such as required retention forceand cost, specific to any one application.

Still another advantage of this invention is that the retentioncomponent optimizes the load transfer between the molding and theencapsulate and allows this load to be spread over a greater surfacearea than conventional heat-stake methods.

Still other benefits and advantages of the invention will becomeapparent to those skilled in the art to which it pertains upon a readingand understanding of the following detailed specification.

III. BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take physical form in certain parts and arrangement ofparts, embodiments of which will be described in detail in thisspecification and illustrated in the accompanying drawings which form apart hereof and wherein:

FIG. 1 is a plan view showing a heat-stake and an encapsulatemechanically coupled according to one embodiment of the invention.

FIG. 2 is a cross sectional view of an encapsulate and retentioncomponent according to one embodiment of the invention.

FIG. 3 is a top view of the sectional view shown in FIG. 2.

FIG. 4 is a cross sectional view of a heat-stake, encapsulate andretention component prior to becoming mechanically coupled according toone embodiment of the invention.

FIG. 5 is a cross sectional view of a heat-stake, encapsulate andretention component mechanically coupled according to one embodiment ofthe invention.

FIG. 6 is a cross sectional view of a heat-stake, encapsulate andretention component mechanically coupled utilizing a hollow stake shapeaccording to one embodiment of the invention.

FIG. 7 is a cross sectional view of a heat-stake, encapsulate andretention component mechanically coupled utilizing a knurled stake shapeaccording to one embodiment of the invention.

FIG. 8 is a cross sectional view of a heat-stake, encapsulate andretention component mechanically coupled utilizing a flush stake shapeaccording to one embodiment of the invention.

FIG. 9 illustrates a prior art heat-stake and encapsulate prior to theheat treatment of a leading end by use of a staking device.

FIG. 10 illustrates a prior art heat-stake and encapsulate showing thedeformation of a leading end of the heat-stake such that a mushroom capis formed.

IV. DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein the showings are for purposes ofillustrating embodiments of the invention only and not for purposes oflimiting the same, FIG. 1 shows a fastened work-piece 10 comprising aheat stake 30, an encapsulate 20, and a retention component 22 accordingto one embodiment of the invention. The heat-stake 30 may comprise abase portion 34 and a shaft portion 32. Shaft portion 32 may bepositioned substantially perpendicular to base portion 34. The angle ofshaft portion 32 with respect to base portion 34 is not intended tolimit the invention as other useful angles will become apparent topersons of ordinary skill in the art. The heat-stake 30 may be formed ofa rigid plastic material such as a polypropylene, nylon, orAcrylnitril-Butadien_Styrol-Copolymere (ABS) or any similar materialchosen with sound engineering judgment. It will be appreciated that theinvention is not limited by the type of material, and that the inventioncan be practiced with any suitable deformable material that can allowthe user to stake the heat-stake 30 in a uniform and consistent manner.The term “stake” is generally applied to a staking operation thatincludes any one of a plurality of fastening methods known in the art,such as conventional welding, ultrasonic welding, and hot staking.

With reference now to FIGS. 1-5, the encapsulate 20 may comprise anencapsulate central passage 24. In one embodiment, the encapsulate 20may be formed of a different material than that used to form heat-stake30. The encapsulate 20 may be formed of a material that is softer thanthat used to form heat-stake 30 or one that has a lower melting point.The hardness of a material may be determined by determining thematerial's indentation hardness, the size of an indention made by anindention tool under a fixed load, or any other method chosen with soundengineering judgment. A material's melting point may be determined byany known method for determining melting point. Similarly, thecomposition of the encapsulate 20 can be varied with respect to thecomposition of the heat-stake 30 based on properties such as vicathardness, apparent melting point, etc.

With continuing reference to FIGS. 1-5, the retention component 22 maycomprise a component central passage 25. In one embodiment, thecomponent central passage 25 may at least partially encircle, surround,or overlap with central passage 24 such that at least a minimum area forallowing the heat stake 30 to be inserted through the encapsulate 20 andthe retention component 22 may be formed. Other embodiments may comprisethe retention component 22 substantially encircling, surrounding, oroverlapping with the encapsulate central passage 24 such that thecomponent central passage 25 is substantially aligned with theencapsulate central passage 24 such that a maximum area for allowing theheat stake 30 to be inserted through the encapsulate 20 and theretention component 22 may be formed. The retention component 22 maycomprise a fastening surface 26. The encapsulate 20 may be formed of arigid plastic material such as a polypropylene, nylon, orAcrylnitril-Butadien_Styrol-Copolymere (ABS) or any similar materialchosen with sound engineering judgment. In one embodiment, the retentioncomponent 22 may be formed of a different material than that used toform the encapsulate 20. The retention component 22 may be formed of aharder material than that used to form encapsulate 20. The retentioncomponent 22 may be attached to encapsulate 20 by an over-molding,co-injection molding, or two-shot molding process or any process chosenwith sound engineering judgment.

With continuing reference to FIGS. 1-5, the shaft portion 32 extendsthrough the encapsulate central passage 24 and the component centralpassage 25. The retention component 22 may substantially encircle theencapsulate central passage 24 as well as the shaft portion 32. Theshaft portion 32 may have a shaft diameter D1, shown in FIGS. 4-5, thatis less than the component passage inner diameter D2, shown in FIG. 2.The encapsulate central passage 24 may have an encapsulate centralpassage inner diameter D3, shown in FIG. 2, that is greater than thecomponent passage inner diameter D2 but less than the retentioncomponent outer diameter D4. Other embodiments of the invention includethe retention component 22 having a component passage inner diameter D2equal to the encapsulate central passage inner diameter D3. And yetother embodiments of the invention include component passage 25 having acomponent passage inner diameter D2 greater than the encapsulate centralpassage inner diameter D3. The cylindrical shape of the shaft portion32, the retention component 22, the component passage 25, and theencapsulate central passage 24 is not intended to limit the scope of theinvention and any shape, chosen with sound engineering judgment, may beused.

With reference now to FIGS. 1-8, the staking operation may be performedby attaching the retention component 22 to the encapsulate 20. In oneembodiment, the retention component 22 may be attached to theencapsulate 20 by an over-molding process. In another embodiment, theretention component 22 may be attached to the encapsulate 20 through aco-injection molding process. Any known method for attaching theretention component 22 to the encapsulate 20 may be used chosen withsound engineering judgment. The leading end 36 of heat-stake 30 may thenbe inserted through the encapsulate central passage 24 and the componentcentral passage 25 such that the retention component 22 at leastpartially encircles shaft portion 32. In one embodiment, a shapingdevice (not shown) may first be heated and then applied to the centralportion 38 of shaft portion 32 about leading end 36 of heat-stake 30.The shaping device transfers heat to the heat-stake 30 thereby softeningthe shaft portion 32 while substantially simultaneously shaping theshaft portion 32 to form a deformed portion 40. Other embodiments maycomprise applying heat directly to the shaft portion 32 and utilizing astaking device (not shown) to deform shaft portion 32 verticallydownward and radially outward about the vertical axis V toward thefastening surface 26 of the retention component 22. The heat may beapplied in the form of hot air or any other known method chosen withsound engineering judgment. The deformed portion 40 may comprise amushroom-cap shape or any other shape that enables the mechanicalcoupling of heat-stake 30 and encapsulate 20 such as a hollow stakeshape 41 (FIG. 6), a knurled stake shape 42 (FIG. 7), or a flush stakeshape 43 (FIG. 8). Inherent characteristics that may contribute to theresulting shape of deformed portion 40 include the material used tocomprise heat-stake 30 as well as shaft diameter D1 of shaft portion 32.The shaft diameter D1 may be of sufficient thickness so that thedeformed portion 40 engages substantially the entire area comprising thefastening surface 26. The shaft diameter D1 may be of any thicknesschosen with sound engineering judgment. Because the shaft portion 32 hasa generally solid outer surface 39, once deformed it applies asubstantially uniform and continuous pressure to the fastening surface26, thereby providing a generally fastened work-piece 10.

Various embodiments have been described, hereinabove. It will beapparent to those skilled in the art that the above methods andapparatuses may incorporate changes and modifications without departingfrom the general scope of this invention. It is intended to include allsuch modifications and alterations in so far as they come within thescope of the appended claims or the equivalents thereof.

1. A method of manufacturing an assembly by heat staking comprising thesteps of: (a) providing a work-piece comprising first and second parts;(b) providing a thermoplastic heat stake comprising a base portionattached to the first part and a shaft portion that extends from thebase portion; (c) providing a thermoplastic encapsulate attached to thesecond part and comprising at least a first opening; (d) over-molding orco-injection molding a thermoplastic retention component onto thethermoplastic encapsulate, wherein the retention component has apassage; (e) after step (d), inserting the shaft portion having a firstend through the first opening so that the first end extends through thefirst opening and through the passage in the thermoplastic retentioncomponent so that the first end extends beyond the first opening and thepassage; (f) after step (e), heating the first end of the inserted shaftportion; and; (g) after step (f), deforming the heated first end of theinserted shaft portion to at least partially overlap the thermoplasticretention component and to connect the first part to the second part. 2.The method of claim 1, wherein step (d) comprises the step of:over-molding or co-injection molding the retention component of acomposition that is harder than the thermoplastic encapsulate.
 3. Themethod of claim 1, wherein step (d) comprises the step of: using anover-molding process to attach the retention component to thethermoplastic encapsulate.
 4. The method of claim 1, wherein step (d)comprises the step of: using a co-injection molding process to attachthe retention component to the thermoplastic encapsulate.
 5. The methodof claim 1, wherein step (b) comprises the step of: forming thethermoplastic heat stake of a composition that is harder than thethermoplastic encapsulate.
 6. The method of claim 1, wherein step (b)comprises the step of: forming the thermoplastic heat stake of acomposition that has a higher melting point than the thermoplasticencapsulate.
 7. A method of manufacturing an assembly by heat stakingcomprising the steps of: (a) providing first and second automotiveparts; (b) providing a thermoplastic heat stake comprising a baseportion attached to the first automotive part and a shaft portion havinga first end that extends from the base portion; (c) providing athermoplastic encapsulate attached to the second automotive part andhaving a first opening; (d) over-molding or co-injection molding athermoplastic retention component onto the thermoplastic encapsulate,wherein the retention component has a passage and is adjacent the firstopening; (e) after step (d), inserting the shaft portion through thefirst opening so that the first end extends through the first openingand through the passage in the thermoplastic retention component so thatthe first end extends beyond the first opening and the passage; (f)after step (e), heating the first end of the inserted shaft portion;and, (g) after step (f), deforming the heated first end of the insertedshaft portion to at least partially overlap the thermoplastic retentioncomponent and to connect the first automotive part to the secondautomotive part.
 8. The method of claim 7, wherein step (d) comprisesthe step of: over-molding or co-injection molding the retentioncomponent of a composition that is harder than the thermoplasticencapsulate.
 9. The method of claim 7, wherein step (b) comprises thestep of: forming the thermoplastic heat stake of a composition that isharder than the thermoplastic encapsulate.
 10. The method of claim 7,wherein step (b) comprises the step of: forming the thermoplastic heatstake of a composition that has a higher melting point than thethermoplastic encapsulate.
 11. The method of claim 7, wherein step (e)comprises the step of: over-molding or co-injection molding theretention component such that the retention component substantiaencircles the first opening.
 12. The method of claim 7, wherein step (e)comprises the step of: using an over-molding process to attach theretention component to the thermoplastic encapsulate.
 13. The method ofclaim 7, wherein step (e) comprises the step of: using a co-injectionmolding process to attach the retention component to the thermoplasticencapsulate.
 14. The method of claim 1 wherein: step (d) comprises thestep of: providing the retention component with an upper surface thatdefines a fastening surface; and, step (g) comprises the step of:engaging the entire upper surface of the retention component with thedeformed portion of the shaft portion.
 15. The method of claim 7wherein: step (d) comprises the step of: providing the retentioncomponent with an upper surface that defines a fastening surface; and,step (g) comprises the step of: engaging the entire upper surface of theretention component with the deformed portion of the shaft portion. 16.The method of claim 1 wherein: step (c) comprises the step of: providingthe first opening with a first diameter; step (d) comprises the step of:providing the passage with a second diameter that is less than the firstdiameter; and, step (d) comprises the step of: extending a portion ofthe retention component within the first opening of the thermoplasticencapsulate.
 17. The method of claim 7 wherein: step (c) comprises thestep of: providing the first opening with a first diameter; step (d)comprises the step of: providing the passage with a second diameter thatis less than the first diameter; and, step (d) comprises the step of:extending a portion of the retention component within the first openingof the thermoplastic encapsulate.